1. Field of the Invention
This invention relates to the field of explosive detection, particularly in the area of trace detection and forensic evidence collection.
2. Description of Related Art
Explosives are essential components of conventional, chemical, biological and nuclear weapons as well as improvised terrorist devices such as car bombs, letter bombs, luggage bombs and personal or suicide bombs.
There are several methods and devices currently operating to detect explosives, and each has its own special application and optimum operating environment. Generally speaking, there are two principal categories of explosive detection techniques: bulk detection and trace detection.
Bulk detection is usually macroscopic in nature, and often carried out by viewing images provided by x-ray radiographic equipment or related imaging technology such as computed tomography (CT).
Another popular method of identifying articles and/or individuals associated with explosives includes the use of canines. The deployment of dogs to discover or track explosives has its advantages and disadvantages. On the negative side, persons subjected to canine inspection may feel threatened or offended. Besides, the liability attached to such inspections is obvious. Moreover, dogs have duty cycle limits, in that they are limited to but one hour of work without a break. Perhaps the most significant limitation to their usefulness is their inability to communicate to the handler the type of explosive detected.
On the positive side, dogs can be conditioned to track and identify almost any substance that is volatile, and with impressive accuracy. More importantly, dogs have at least the capacity, though limited, to make a physical connection between a detected substance and its associated human source. More recently, honeybees are being preconditioned to make targeted discoveries during their wide-ranging foraging efforts. University of Wyoming researchers in this area train bees to find such targets as explosive material and drugs.
Another method of testing for the presence of explosives involves bulk detection by x-ray imaging of a container or package so as to discover metal parts used in fuzes and/or wiring required for proper functioning. Still another method involves neutron activation of the chemical elements such as carbon, oxygen and nitrogen that make up the explosives.
Regardless of method or device, responsive and reliable explosive detection development remains a priority in the present climate of global terrorism. For a number of reasons, significant research and developmental resources are shifting to trace evidence tracking and discovery. This is particularly the case since interpretation of X-ray or CT images is highly labor intensive and subjective. The result of this shift is the emergence of varied embodiments of trace detectors that are highly effective in discovering minute amounts of explosive.
Typical of such trace detection techniques are systems involving Ion Mobility Spectrometry (IMS), Chemiluminescence, Electron Capture Detectors (ECD), Surface Acoustic Wave Sensors (SAW), or system combinations such as ECD and Chemiluminescence detectors, or SAW and front-end Gas Chromatograph (GC).
Then, too, there are the Thermo-Redox detectors and a technique called Field Ion Spectrometry. Perhaps more well known are the highly developed Mass Spectrometry systems, and the recently developed EXPRAY field test kit. Still other relatively newer techniques or devices for trace detection have emerged in the form of the Thermal Neutron Activation (TNA) system, the 14.7 MeV neutron interrogation system, and the Pulsed Fast Neutron Analysis (PFNA) technique currently under development by SAIC, Inc.
More techniques under recent development include the Quadrupole Resonance (QR) technique (developed by Quantum Magnetic Inc.), and the Portable Isotopic Neutron Spectroscopy (PINS) chemical assay system developed jointly by EG&G Ortec, Inc. along with the Idaho National Engineering and Environmental Laboratory.
Current methods for detecting explosives on humans, particularly when they are entering portals to transportation systems or important facilities, include the removal of particulates by air blasts directed toward possibly contaminated areas such as hands, pockets, belt area and handbags, and subsequently capturing the residue.
The air blast and particulate capture in such systems are followed by pre-concentrating and heating the residue and detecting the unwelcome substance by employing one or more of the many sensitive techniques such as Ion Mobility Spectrometry (IMS), Gas Chromatography (GS), Mass Spectrometry (MS) and other such processes.
These systems and methods are typical of those commonly used when inspecting people and/or their baggage or other personal items. For example, passengers entering air or ground transit, as well as attendees at a massive ticketed event, find themselves subjected to this type of inspection. However, such systems and methods are only as effective as the time or opportunity allowed for such inspection. At best, such inspections can be intrusive; at worst, even abusive.
Obviously, in the interest of time, efficiency, and human comfort, everyone in a card/pass holder queue cannot be tested by these complex systems. Currently, inspections must be limited to subjects randomly selected (or pre-identified by some form of prescreening technique) so as to avoid disturbing and/or delaying the entire card/pass holding queue. Besides the issue of time, there are further issues of logistics, physical layout for the equipment, trained supervised staffing and so forth.
Under constraints of time and space, and the ever-present need to avoid obstructing passenger or patron traffic, the tasks of capturing and evaluating trace evidence are vexing. The challenge becomes insurmountable with the growth of demand for reliance on such inspections and with the constant expansion of facilities that require such safeguards. Hence, these trace evidence discovery systems are becoming ubiquitous.
According to the National Institute of Standards and Technology (NIST), around 20,000 IMS units currently are deployed worldwide, with more than 7000 of those placed at US airports. Vast numbers of units are in place at embassies, stadiums, courthouses, and so on. The demand for enhanced security at every turn is exploding. With this explosion, there is a growing need to strengthen metrology and develop reliable standards to support ever-widening deployment. Even as trace detection quality is refined, the overall methodology currently in place is flawed for a number of reasons.
Current trace detection processes, regardless of the substance residue testing method, usually require detention or retention of persons, luggage, and so forth identified through earlier screening processes as persons or items of interest. Pre-screening, as by profiling or behavioral observation, obviously has its limitations. Current trace discovery technology also has its limiting issues. Such techniques are not always successful due to the lack of sufficient quantity of traces, insufficient time for thorough analysis, or simply because the traces are never easily identified.
Many explosives have a very low vapor pressure making detection particularly challenging to existing technologies. An example of such an explosive is SEMTEX, a plastic explosive manufactured in the Czech Republic. SEMTEX is difficult to trace since it has no detectable smell, and has been used by extremist groups in the Middle East, Libya, Balkans and by the IRA in Northern Ireland.
Other low vapor pressure explosives particularly challenging to existing trace discovery technology are pentaerythritol tetranitrate (PETN) and hexahydro-trinitro triazine (RDX), both commonly employed in terrorist bombings. These can easily be molded for concealment. Only relatively small amounts of these substances can bring down large aircraft, destroy buildings and wreak havoc on rail transit systems.
Examples of techniques and apparatus for detecting the presence of trace evidence of explosive abound. With respect to the present invention, the more pertinent documents uncovered in patent literature searches are embodied in the following patent documents.
Haley et al., in U.S. Pat. No. 5,760,898, disclose a technique for detecting traces of explosive material, for example on a suitcase, by applying laser radiation to the surface thereof. This causes micro-detonation of any trace particles thus enabling detection of the explosive by its characteristic emission.
In U.S. Pat. Nos. 5,638,166 and 5,912,466 issued to Funsten et al., a photomultiplier, a charge couple device or a photodiode is used to detect ultraviolet emissions resulting from heating of explosive purportedly resulting in deflagration. An apparatus and method presented by Sousa et al. in their U.S. Pat. No. 5,364,795 may be employed to detect the presence or absence of propellants, explosives, and nitro pollutants, wherein a laser photon fragments a target molecule and facilitates detection of the characteristic NO fragment.
Laser energy is also key to the detection system of Brestel et al. disclosed in Published US Patent Application No. 2004/0051867, wherein at least one laser illuminates a portion of an object and either a second harmonic detector or a luminescence controlled substance detector, or both are used. Additionally, the Brestel et al. system includes a Raman scattering based substance detector.
Megerle's U.S. Pat. No. 6,610,977 discloses a method and apparatus for screening an object for the presence of an explosive, chemical warfare agent, biological warfare agent, drug, metal, weapon, and/or radioactive material. The apparatus includes a portal through which the object is arranged to pass, the portal including a housing equipped with an ion mobility spectrometer and a surface acoustic wave device for detecting explosives, drugs and chemical warfare agents. In another embodiment the housing is equipped with a biological warfare agent detector, chemical warfare agent detector, metal detector, x-ray system, and/or radiation detector.
Nguyen et al., in U.S. Pat. No. 6,797,944, disclose a laser desorption and detection of explosives, narcotics and other chemical substances. The Nguyen et al. technique employs a compact scanning apparatus including an optical system to deliver a beam of pulsed infrared laser light that illuminates an interrogation area of the surface.
The illumination described by Nguyen et al. is sufficiently intense and of such duration as to cause selective ablation of molecules of contraband substance present on a surface without substantially damaging the surface. A portion or sampling of the ablated molecules is collected and transferred to a separate chemical analysis system where a detector reacts to the sampled portion and activates an audible or visible alarm. A traceable residue of the detected contraband is left on the article for subsequent forensic analysis.
In EPO455516, Akery et al. present a security system for an airport or the like where an item such as a ticket or a boarding card is checked to see if it holds traces of explosive or other contraband picked up from the passenger's hands. According to the invention, a prospective passenger is handed a boarding card, landing card, identity card or like item for use in gaining passage beyond a check point. The card or like item is such as to absorb traces of explosives and other contraband material from the passenger's hands should such traces be present thereon.
After the card has been handled by the passenger, Akery et al. explain that at least part of the card is tested for the presence of any of said traces. Before boarding the aircraft, passengers are required to insert their cards into a card analyzer. This analyzer consists of apparatus for determining the presence of trace levels of single or multiple explosive types from the surface of the card.
The analysis in the Akery et al. patent may include heating the surface of the card and passing the desorbed particles into a Grace Gas Analyzer. Alternatively, the analysis may employ a liquid or gaseous solvent to remove the absorbed materials from the surface preceding trace chemical analysis. The chemical analysis may include mass spectrometry, gas chromomatography, ion mobility spectrometry, etc.
The magnetic strip on a card also is read in a reader/analyzer and the information thereon passed to the airline's computer system, as further disclosed by the Akery et al. patent. The presence of explosives and the card holder's identity are indicated on a monitor to security staff who can take appropriate action.
In U.S. Pat. No. 5,818,047, Chaney et al. also address airport security. The Chaney et al. patent disclosure focuses in particular on SEMTEX plastic explosive in a sample such as a fingerprint. The explosive trace is detected by Raman spectroscopy as a boarding card is fed into a boarding card reader for otherwise normal processing prior to boarding.
The Chaney et al. patent explains that as the boarding card is transported by the boarding card reader, it is scanned by a laser, for example, a gas laser such the Helium-Neon type. A dichroic filter reflects the laser light and focuses it on the card. Filtered Raman scattered light is collected and focused by a lens onto a detector, such as an avalanche photodiode. This detector reacts to indication of the presence of explosive trace.
One particular advantage of the Raman analysis technique employed by Chaney et al. is that it is non-destructive. Hence, if SEMTEX explosive substance is detected, the card can be retained for further analysis and for use as evidence. Such systems can be modified for detecting SEMTEX explosive material on other surfaces such as tickets, identity cards, passports, and so forth. Further, according to Chaney et al., such systems may be used in situations other than an airport boarding card reader, e.g. at the entrances to public buildings, government offices and the like. The non-destructive nature of the Raman analysis lends itself to such situations, since the ticket, card and such can be handed back to the holder after analysis.
To enhance the performance of the Chaney et al. system, the patent disclosure suggests coating the card with a thin layer of a material such as silver, gold or copper, and providing it with a suitably roughened surface such that molecules of substances such as RDX or PETN will be adsorbed onto the roughened surface and would thus exhibit surface enhanced Raman scattering.
Valentinovich et al., in Published US Patent Application 2004/0124376, disclose a system and an apparatus for detecting explosive in real time. The apparatus involves a chamber in which items pass through or people walk through for detecting said explosive particles in real time. The explosive particles from either the people or items will be deposited into a cell by an influx of air flow from the chamber to the cell.
The cell described by Valentinovich et al. includes a heating device and an optical scheme. The cell is heated to a predetermined temperature in which the explosive particles are divided into small molecular components that can be detected. The optical scheme detects the smaller molecules. The computer system controls the apparatus and analyzes the data gathered.
These old and more recently developed systems and techniques, as just described, have unique strengths and shortcomings. The latter reflect a lack of adaptability to field application, particularly with respect to challenges presented by fast-moving masses of people passing checkpoints or dealing with automated ticket collectors for transit systems and major events across the country and across the planet.
Attempts to apply existing technologies in solving the myriad of issues in this field result in the construction of highly complex and relatively expensive systems. They demand well-trained, highly skilled and experienced personnel and require constant, personal monitoring and participation. Too often, subjective judgment must be relied upon. And, importantly, few if any of these systems (other than the trusty canine) can establish a direct link between discovered trace evidence and the human perpetrator.
The invention presented herein as the subject of this application addresses the above noted problems and shortcomings in a unique manner, while drawing upon off-the-shelf detection and analysis technologies assembled and applied in a new and unobvious manner and achieving wholly unexpected results. To achieve this, the present invention takes advantage of some basic principles observed with respect to explosive trace evidence, but not heretofore exploited in the trace detection field.
As demonstrated by the prior art discussed hereabove, it is well known that surfaces brought into contact with commercial, military or improvised explosives become contaminated with traces of explosive particulates. Such surfaces may include, but are not limited to, luggage coverings, purse fabric, and bare skin, as well as tickets, boarding passes, electronic key cards, passports and the like which typically are presented for facility entry, passage to major events, or boarding transit conveyances or systems.
Trace evidence contamination may have its origins during explosive manufacturing, packaging or subsequent handling stages of such explosives. Also, the explosive-related contaminants are well known to be sticky in nature, thus having a tendency to linger on the handlers' hands, particularly within skin patterns such as typical fingertip whorls, loops or arches. The stubborn, sticky contaminants often will remain on the hands and other surfaces of interest for several hours despite repeated washing.
The proposed technique employed with respect to the present invention includes direct observance of yet another property common to explosives. Upon detonation, all explosives undergo an exothermic reaction resulting in the generation of significant heat. In minute traces, explosion is not likely since the dimension of explosive particulate is less than a diameter critical to sustained detonation. However, explosive material in very small sizes or traces will, when subjected to a rapid heating process, deliver a relatively large amount of heat whether it detonates or deflagrates. Sufficient heating is certain to bring about an energetic, if not sustained, reaction.
In the present invention, one of the techniques to initiate or activate an explosive trace involves heating a trace evidence on a substrate to a temperature higher than the critical temperature where an exothermic reaction would set in, but not so high that the substrate is destroyed. The intent herein is to employ heat in driving the explosive substance to react in such a way that the resultant reaction delivers an identifiable signature to the substrate, as will be explained.
As inferred hereabove, the fingers or other portions of the hands of a person working with explosives typically will carry or retain at least a few micrograms of explosive residue. Despite all determined efforts to avoid it, fingerprints of explosive handlers invariably will be transferred to any surfaces or items touched or handled, as for example boarding passes, tickets, coupon, transit transfers, key cards, currency, fare cards and the like.
As an example, it has been recognized that fare cards employed to access mass transit trains such as London's Tube, the Metro transit lines running in Washington, D.C., or the Subway system in New York City and similar mass transit systems in other metropolitan areas can be found to carry trace evidence of explosive residue. Boarding passes (generally in the form of cards) for gaining access to aircraft or long distance passenger trains could also carry similar residue-contaminated fingerprints. Finger prints, however, generally are invisible to the unaided eye, even if they contain explosive trace evidence. While latent fingerprints may be revealed or made more visible through application of vapors of iodine or by Superglue®, neither application will be successful in detecting explosive traces.
Testing for explosive traces on boarding passes and fare cards has been postulated in the past; however, the question remains: How best to deal with such trace evidence in an effective and efficient manner, and in a way that is essentially nondestructive such that forensic evidence is retained. Further questions: a. how best to do this in real time and automatically, and in such as way as to avoid traffic disruption or excessive invasiveness; b. how best to test for explosive traces and unequivocally tie such traces to a perpertrator?
Fare computations, e.g., date/time, points of embarkation and destination, and other data, presently are routinely read by well-known automatic scanners at subway turnstiles and airline boarding gateways. In some instances as discussed above, trace explosive evidence on boarding passes purportedly has been detected by sophisticated scanning devices such as the Raman Spectroscopy or ablation by lasers and the characteristics of the ignition evaluated. However, while such data are read by scanners, no method currently exists to actually capture or reveal fingerprints directly associated with or related to such evidence.
Thus, while fingerprints (and/or prints of other portions of the hand) contaminated by explosive trace evidence most likely appear on fare cards and boarding passes, processes for capturing the trace in situ and reading or capturing the prints did not exist prior to the present invention. Further, until the present invention, there was no known technique or system by which trace evidence could be analyzed in real time and without significant passenger traffic disruption (e.g., during a normal scan/read operation of a transit fare card and the like) and in such a way as not to result in bottlenecks at gateways or turnstiles.
Department of Homeland Security (DHS) experts naturally have identified such gateways as crucial to protection of a threatened public. Up to this point in time, general thinking has dictated that, even if trace evidence could be captured and evaluated, such a complex process would be far from convenient or economically feasible, and thus would be rejected as raising unacceptable barriers and cost margins for the traveling public.
Until now, and without extensive, laborious and individually-targeted screening techniques, singling-out individuals as they are queued for passing portals and perhaps carrying trace evidence of explosive handling has been impractical and far from cost effective. There is a long felt need for an automated system and process for examining substrates, articles or material touched and handled by individuals, and capturing evidence instantly linked to a bearer who also handled explosive materials. This also must be a real-time technique applied as subjects are constrained to pass, one by one, through a validation checkpoint (e.g., airport gateway, transit turnstile, entrances to pavilions, concert halls, civic centers and the like).
The requisite presentation of Metrocards®, fare cards, boarding passes, tickets, passports and the like by people queued at a checkpoint, turnstile or gateway for travel or events offers distinct opportunities for gathering trace evidence, since such cards, passes and the like must be physically handled by their bearers or presenters.
The present inventive system and process effectively resolves the shortcomings and inadequacies of the prior art in satisfying the long felt need.